// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_BASE_MOVING_AVERAGE_H_
#define MEDIA_BASE_MOVING_AVERAGE_H_

#include <stddef.h>
#include <stdint.h>

#include <vector>

#include "base/macros.h"
#include "base/time/time.h"
#include "media/base/media_export.h"

namespace media {

// Simple class for calculating a moving average of fixed size.
class MEDIA_EXPORT MovingAverage {
public:
    // Creates a MovingAverage instance with space for |depth| samples.
    explicit MovingAverage(size_t depth);
    ~MovingAverage();

    // Adds a new sample to the average; replaces the oldest sample if |depth_|
    // has been exceeded.  Updates |total_| to the new sum of values.
    void AddSample(base::TimeDelta sample);

    // Returns the current average of all held samples.
    base::TimeDelta Average() const;

    // Returns the standard deviation of all held samples.
    base::TimeDelta Deviation() const;

    // Resets the state of the class to its initial post-construction state.
    void Reset();

    size_t count() const { return count_; }

private:
    // Maximum number of elements allowed in the average.
    const size_t depth_;

    // Number of elements seen thus far.
    uint64_t count_;

    std::vector<base::TimeDelta> samples_;
    base::TimeDelta total_;
    uint64_t square_sum_us_;

    DISALLOW_COPY_AND_ASSIGN(MovingAverage);
};

} // namespace media

#endif // MEDIA_BASE_MOVING_AVERAGE_H_
